Illuminated signs are used throughout the world to convey information to passers-by. Neon is often chosen for such illuminated signs because of the distinctive, brilliant color it emits. Traditionally, neon has been used in the form where tubing is bent into the shape of a word. Manufacture of this type of sign requires the frequently costly services of a skilled glass tube bender. Such signs are also limited in that once they have been created at considerable expense, they cannot be modified.
Referring now to FIGS. 1 and 2, there are depicted a partial-cutaway plan view and a cross-sectional side view of an illuminated sign, known as a neon grid sign, described generally in several early U.S. patents (for example, U.S. Pat. No. 1,813,759 to Thomas Peters, U.S. Pat. No. 2,080,679 to E. D. Vissing, U.S. Pat. No. 2,094,436 to H. R. VanDeventer et al., U.S. Pat. No. 2,046,044 to R. A. Vissing, and U.S. Pat. No. 2,118,385 to J. J. Shively). Such signs are not prevalent in commerce today. Sign 10 comprises essentially a sign frame 14 having a width "W" in which are located lengthwise sections of luminous tubing 12 parallel to the width and providing illumination. The sign frame is covered by a sign face 18 having transparent letters 11 outlined by an opaque background 13.
Luminous tubing 12 has a small diameter relative to the sign box width, and thus may be bent in alternating 180-degree curves into an S-shaped pattern with lengthwise sections 15 between curves 42 to provide illumination over the complete sign width, as shown in FIG. 1. The luminous tubing 12 is electrically attached to an electrical transformer 16. To provide a uniform appearance of light instead of a series of lines, the tubing may be mounted within curved, reflective channels 20 that have a mirrored surface.
A neon grid signs offers an advantage over signs comprising merely a neon tube bent into the shape of a word, in that a single sign frame 14 may be used with multiple or modifiable sign faces 18 to change the text of the sign as desired. The neon grid signs as described in the aforementioned references have a disadvantage, however, in that from certain angles between the viewer and the sign, the light shining through the letters forms a streaked pattern, as depicted in FIG. 3, that make the message on the sign difficult to read. Depending upon the quality of the reflectors behind the tubing, this streaked pattern may appear as a series of dark lines, or may comprise stripes of greater and lesser brightness.
The unilluminated ridges 22 between reflective channels 20 may contribute to the streaked pattern. A key factor in the creation of the streaked pattern is that the curvature of the reflector 20 may not reflect light back to the viewer 30 from the tubing 12 at certain viewing angles .gamma., as shown in FIG. 4, but instead reflects the lesser light coming from the direction of the viewer.
Some of the references disclosed above discuss ways to address this problem. Patent '759 describes a neon grid sign where the grid of neon tubing stands alone as the source of light, and where the pattern produced by either a single grid of one color, or multiple grids of more than one color is part of the effect desired. In such a pattern, the changes in color or light intensity are desired, so the issue of uniform light is not addressed.
Patent '679 describes the presence of metallic reflectors similar to reflectors 20 that reflect the light from the neon tubing in what is "practically a sheet of light". Patent '679 also describes, however, some presence of dark lines or reduced light reflection efficiency associated with each reflector embodiment. Significantly, patent '679 also refers to means for angling the sign to enable the sign to be more easily read when the observer is above or below the sign, implying that the illumination quality may suffer when the sign is at a vertical angle from the viewer.
Patent '436 purports to provide a sheet of neon "substantially free of the objectionable streaks and of uniform over-all brilliancy"; however, the reference provides no detail regarding the geometry of the reflectors, so that this claim can be verified. Additionally, the patent claims adjustable means for tilting the sign face at various angles, again suggesting that the sign may have required angular adjustment to facilitate streak-free viewing at certain angles.
Patent '044 describes an improvement in the form of a gap in the reflector that was necessary to prevent electrical buzzing from occurring as a result of current leakage from the bulbs to the metal reflectors.
Patent '385 describes a neon grid sign that uses a sheet of ribbed glass or other diffusion plate to help eliminate the streaked pattern. Such a diffusion plate, however, necessarily also dims the brightness of the light visible to the viewer. Thus, some of the color and brilliance that makes neon a desirable light source may be lost.
The continued pursuit of a neon grid sign free of the undesirable streaked pattern in the 1930's and the dearth of such signs in commercial use today are testimony to the desirability and elusive nature of a sign that eliminates the streaked pattern. The present invention provides a neon grid sign and method for designing such a sign that optimizes the dimensional properties of the reflector channels to eliminate, without a diffusion plate, the streaked pattern even when the sign is viewed from a vertical angle, the reflector channel design being adaptable to the largest viewing angle of the intended viewer.